From: Hazel Davey (hlr@aber.ac.uk)
Date: Wed Sep 30 1998 - 05:36:07 EST
JCS wrote: > > Hi, > > I am a newbie to this newsgroup, so don't mean to intrude. I have a question > about hemacytometer: I am thinking of getting one to count the number of > cells cultured in my experiment (degradation study of biomaterials). Now, > how many cells does one usually count to achieve a high precision rate? The percentage error associated with haemocytometer counts is usually quoted as: + or - 100 / SQRT(n) where n is the number counted. Most people count only a few hundred cells so the errors are huge: n=100 -> error = +/-10% n=500 -> error=+/-4.5% A count of >10,000 is required to get errors below 1% - I doubt very much that it's ever been done!! This is of course under ideal conditions i.e. excluding errors of diluting the sample to the correct concentration / loading the haemocytometer / errors in counting the number of dots infront of your eyes etc > I am > also afraid that in order to achieve an uniform distribution of cells before > counted, a shake or two is required--->and wouldn't this tear up some cells > due to shear forces, etc? This will depend on the type of cells that you are using and the treatments that they've been exposed to. If accurate counts are important to you I'd find another way if you can! Haze ---------------------------------------------------------- | Hazel Marie Davey hlr@aber.ac.uk | |Sefydliad y Gwyddorau Biolegol*Inst. Biological Sciences| |Prifysgol Cymru * University of Wales| | ABERYSTWYTH, Ceredigion, CYMRU / WALES SY23 3DD | | http://pcfcij.dbs.aber.ac.uk/index.htm |
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